Not Applicable
Not Applicable
1. Field of the Invention
The present invention relates to electrohydraulic control valves, and more particularly to such valves which incorporate a balanced poppet.
2. Description of the Related Art
In an effort to improve fuel economy, automobile manufacturers have devised systems that deactivate selected engine cylinders when the full power produced by all the engine cylinders is not required. For example, Cadillac introduced the xe2x80x9cV-8-6-4 enginexe2x80x9d which switched between 4, 6 and 8 cylinder operation. The selection of which cylinders to deactivate is determined by engine firing order with the desire to keep an even firing order in the deactivated mode. Several modes of cylinder deactivation are possible. In a bank mode, the multiple cylinders in the same bank of a V configuration engine are switched at the same time, whereas each cylinder is switched independently in the cylinder control mode. A given cylinder is activated and deactivated by controlling the operation of the intake valves for that cylinder. By disabling the intake valve or valves for a given cylinder, the air-fuel mixture does not enter that cylinder and thus combustion does not occur
Some engine designs employ multiple intake valves through which an air-fuel mixture is supplied to the cylinder. Fuel conservation also can be achieved by selectively switching operation of different numbers of the intake valves for a given cylinder.
The engine intake valve operation is controlled by a solenoid valve which governs the flow of pressurized engine oil to an intake valve actuator. When the solenoid valve energized, pressurized engine oil is applied from a work port to operate a spring biased locking pin inside the intake valve lifter, which effectively decouples the cam shaft from the cylinder intake valve. When the solenoid is de-energized, the valve""s work port is connected to the engine oil sump removing the pressure to the intake valve actuator which results in a spring biasing the locking pin to activate the intake valve.
It is desirable to control the switching of the engine intake valves in less than one engine cycle. Therefore, the solenoid valve must respond very quickly in order to ensure timely deactivation and reactivation of the engine cylinder valve. Thus, it is desirable that the solenoid valve is required to generate as little force as possible thereby minimizing operating time.
An electrohydraulic control valve is provided to control the flow of engine oil which has a nominal pressure. That control valve includes a tubular valve body with a longitudinal bore there through and forming an outlet port at one end of the valve body. An inlet port and a work port extend transversely through the valve body opening into the longitudinal bore. A first valve seat is located in the valve body between the inlet port and work port, and second valve seat is located between the work port and the outlet port.
A poppet is received within the bore of the valve body and is able to move between a first position at which the poppet engages the first valve seat and a second position at which the poppet engages the second valve seat. A notch is formed in a portion of the poppet that is adjacent the inlet port so that the pressure of the oil in the inlet port acts on the notch surfaces. The notch has a first end surface on which pressure in the inlet port exerts a first force that tends to move the poppet into engagement with the first valve seat. The notch having a second end surface on which pressure in the inlet port exerts a second force that tends to move the poppet into engagement with the second valve seat. A spring which provides a spring force that biases the poppet into engagement with the first valve seat.
An actuator of the valve includes a solenoid coil wherein application of electric current to the solenoid coil moves an armature that engages the poppet. That action causes the poppet to move away from engagement with the first valve seat and into engagement with the second valve seat.
The first and second end surfaces of the notch in the poppet are so designed wherein the nominal pressure in the inlet port acting on those surfaces exerts a net force on the poppet which substantially counteracts the spring force. This balancing of forces enables a relatively small actuator to be employed as the actuator need only produce a relatively small force to move the poppet between the first and second valve seats.
Another aspect of the electrohydraulic control valve is a unique design of the valve elements which enable the use of plastic components and ultrasonic welding of those components to facilitate assembly of the valve.